Corrugated metallic conduit and process of making it



J. R. FREEZE 2,017,058 'CORRUGATED METALLIC CONDUIT AND PROCESS OF MAKING Oct. 15, 1935.

Filed Dec. 5, 1930 5 Sheets-Sheet`2 y n' N i mi.

Oct. 15,` 1935.

J. R. FREEZE CORRUGATED METALLIC CONDUIT AND PROCESS OF MAKING IT Filed Dec. 3, 195o 5 sheets-sheet 3 INVENTOR.

am@ BY ATTORNEYS l Oct. 15', 1935. J. R. FREEZE CORRUGATED METALLIC CONDUIT AND PROCESS OF' MAKING IT Filed Deo. 3, 1950 5-Sheets-Sheet 4 O O O O O O ATToRNEYS INVENTOR.

Patented Oct. l5, 1935 D STATES PATENT GFFICE l CGBRUGATED LIETALLIC CONDUIT AND PROCESS MAKING IT application. peeember 41920, serial No. 499,844

l@ (Cl. 2li-148.2)

My invention relates to pipe formed of sheet metal and having transverse corrugations. Such pipe is in widespread public *use as culverts and the like. It is regularly manufactured by taking 5 rectangular pieces of galvanized sheet metal and running them through a pair of corrugating rolls with the longer dimension of the sheet parallel to the axis of the rolls. The rolls are corrugated or fluted longitudinally. The purpose of forming corrugations in the sheet parallel to the longer dimension thereof is to secure suilicient length in the sheet to give the desired circumference to the pipe. 'I'he corrugated sheet is then bent or curved by suitable means into an arcuate form. The usual mechanism employed comprises three transversely corrugated rolls adjustable relatively to each other. In one commercial operation the sheet is bent to form the entire circumference of a conduitl and the ends are riveted together, the length of the conduit being attained by joining together additional sections with the longitudlnal joints in staggered relationship. In another somewhat less common commercial construction corrugated sheets are bent Vinto half circles forming nestable sections, and means are provided for joining the sections together on the job. The corrugations as formed in the sheets comprise circular arcs connected by ltangents. For all gauges of metal the commercial depth of the corrugation is one-half inch, and the pitch or distance between successive crests or .valleys is two and two-thirds inches. All of the machinery employed in culvert plants is designed to fabricate this type of corrugation only. For this reason it has never been deemed feasible to depart from the existing standard, demands for increased strength being met by furnishing sheets of different gauge. y The choice of gauge has largely been determined of course by the size of the nished conduit and the strength requirements which it must meet; but it has not been possible to maintain commercially a completely logical relationship of gauge to size and strength. Commercial culverts `or conduite now range from 16 gauge for the smaller diameter up to 8 gauge for large culverts, bridges and the like. From 60 inches diameter to 120 inches' diameter the gauge remains the same, an obvious inconsistency due to manufacturing difficulties. Thereasons why this isso are inherent in the machinery and processes employed for making culverts. As hereinabove explained, the mechanism for corrugating sheets comprises a heavy pair of corrugating rolls of a length sumcient to accomodate the longest sheet of metal which it is desired to use. Attempts to employ this mechanism for corrugating sheets heavienthan 8 gauge have not been successful because obviously the 5 machinery is not heavy enough. 'Ihe rolls spring, producing corrugations which are shallower in the center of the sheet than at the edges thereof; and the heavy pressure on the rolls in corrugating so thick al sheet results in a V10 disrupting of the galvanized coating thereon and a destruction of its protective eiciency. The same considerations apply to the bending rolls as to the corrugating rolls; and with very heavy sheets,such as those over 8 gauge, the bending 15 rolls themselves disruptthe coating.

My invention relates essentially to culverts of the heavier type. One of its objects is the simplication of the manufacture of such culverts or conduits. In the commercial manufacture of 20 conduit up to say 48 inches in diameter, the sheets after corrugatinghave a width of approximately 24' inches and a length equivalent to the circumference of the conduit plus an allowance for a lapped seam. 'I'he sheets are formed into cyl- 25 indrical sections 24 inches in length and are riveted together in machines especially designed for the purpose. Conduits 'are thus commercially made up in lengths which are multiples of 2 Vfeet.' Where the diameter exceeds say 54 inches,'3o

two sheets and in some cases more are used to form the circumference of a single section. With large diameters it is frequently necessary to provide a pit in front of the riveting machines; and the handling of culvert sections and the building 35 up of lengths of conduit becomes an exceedingly cumbersome operation.

- Another object of my invention is the provision of a process whereby the gauge may follow the size and strength requirements of large size cul- 40 verts. An ancillary object of my invention is the provision of a process of corrugating metal essentially heavier than 8 gauge, and of providing heavier corrugated culvert sections with completely protective galvanized coatings. 45 Still other objects of my invention are the provision of novel conduit sections and conduits formed thereof as will hereinafter be more fully set forth.

These and other objects of my invention which 50 will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications, I accomplish by that certain process and in that certain construction and arrangement of parts of which I shall now describe ex- 55 emplary embodiments, reference being had to the accompanying drawings.

In the drawings:

Figure 1 shows a plurality of my culvert sections nested for shipment.

Figure 2 shows in perspective a representative section of culvert or conduit constructed in accordance with my invention.

Figure 3 shows a representative type of connecting band for a culvert of my constructionj Figure 4 is an elevation of a conduit showing a different method of making connections between sections.

'Figure 5 shows a ilat corrugated plate used in making the cu1vert or conduit of my invention.

Figure 5a is a cross-sectional view of Figure 5.

Figure 6 shows such a corrugated plate curved l to the 'desired radius.

Figure 7 is-a section of a representative corrugated plate.

Figure 8 shows a representative conduit of elliptical shape formed with my sections.

Figure 9 shows a circular conduit formed with my sections.

Figure 10 shows a type of bolt suitable for connecting together the plates to form a conduit of my type or conduit sections as formed.

Figure 1l shows another typeof bolt adapted to a similar purpose.

Figure l2 shows a diagrammatic view of the corrugating rolls.

Figure 13 shows diagrammatically the bending die apparatus.

In the practice of my invention I form a cul- `:vert or conduit from a plurality of curved and corrugated -metal plates `or sheets which plates however, are not bent to constitute the entire periphery of a conduit nor to so great a curvature as would cause them to constitute substan.

tially 180 degrees of the circumference of a conduit; On the contrary my plates as ordinarily formed are intended to constitute no more usually than one quarter of the circumference of the completed culvert for reasons which will herein- Aafter be made plain. In many instances more than four of Amy plates are used in the formation of the full circumference of a conduit.

In meeting the practical problems ofv the formation of heavy corrugated conduits of large Idiameter, I am enabled to corrugate heavier sheet `or plate metal by comigating the said metal along its shorter rectangular dimension, rather than along its longer rectangular dimension, as shown in Figure 5. I am enabled to do this. because I do not intend, after corrugating my sheets or plates, to bend them to a full circle or even to as much as a half circle; but on the contrary I bend my sheets or plates to an arc which is comparatively a small portion of an entire circumference, and I build up a pipe or conduit by joining together Amore than two of such corrugated and curved plates. Corrugating the plates along their shortest dimension permits me to use thicker, heavier and shorter rolls, whereby I can handle heavier metal pieces with entire satisfaction. I have shown in Figure 5 a sheet of metal of heavy character treated so as to present corrugations, having crests 2 and valleys 3 as viewed from the edge in Figure In Figure 7 I have drawn to scale a representative heavy corrugated sheet in which the circular curvature of the valley portions 3 has a 'radius of one inch. The depth of the corrugations, i. e., the vertical distance between a valley 3 and a'crest .2 is 1%'of an inch, while the pitch ordinary corrugations in commercial culverts or conduits. These dimensions however, ar'e exemplary, and are not limiting upon the broader aspects of my invention. They represent merely a type of corrugations suitable for heavy work in culverts or conduits, say inches in diameter. The plate shown as corrugated in Fig'- ure 7 is a piece of six gauge metal. 'I'his also is exemplary and not limiting. I pass the corrugated sheet or plate I through bending rolls or dies so as to curve it into such a configuration as that shown in Figure 6 where the curved sheet is indicated at la. It will be seen that the curvature of the sheet or plate comprises in this instance only a relatively small part of the entire circumference of a circle ofthe same radius, and

substantially less than half thereof. Before or after curving the plate to the form shown in Figure 6, I prefer to form in it; by punching or otherwise, a series of holes I which may be used for the passage of bolts or rivets infastening plates together in theformation of the full circumference of a circular or other-shaped section of conduit.

In practice, I pass my blank sheets longitudinally through a pair of corrugating rolls, as

shown in Figure 12, and indicated at 30 and 3l.

Viewed in cross-section, these rolls give the appearance of a pair of mating gears, and thetooth contour is the desired corrugation. The

two stationary supports 33 and 34,v and in which the stroke of the ram may be adjusted as desired` in any well known way. I insert one longitudinal edge of the sheet into the machine, and give it a slight curvature by means of the ram. I`

then advance the sheet further into4 the machine in the direction indicated by the arrow and give it a further curvature; a total of three or four bends as above described will suice to give my sheet the desired curvature. Obviously the stroke of the ram, or the number of bends given the sheet, is in no way to be considered as a limitation upon my invention, since the greater the stroke, and the more the bends, the greater will be the ultimate curvature of the sheet. The above mentioned operation is hereinafter also referred to as bending by means of a die.

It is a distinct advantage of my invention that through the steps hereinabove described of form-- ing my plates, I am enabled with particular ad.. vantage to do the coating or galvanizing of the plates after their formation as hereinabove described and after their perforation for the passage of bolts or rivets. Conduits have been made which have been galvanized after their mechanical formation; but the galvanizing operation isl inconvenient and cumbersome due to the diiliculty of handling completed structures, and is uneconomical due to the length of time involved in it and the difficulty of satisfactorily draining away excess zinc from the convolutions of such completed structures. In galvanizing after fabrication such structures as are shown in my Fig- 4 ing pot or the like, mechanically immersed beneath the surface of the coating metal and mechanically removed therefrom. They do not present a drainage diiliculty inasmuch as it is only necessary to remove them from the` galvanizing bath along a circular path of movement having a radius not substantially greater than the radius of curvature of the plates themselves. When so removed,l they drain readily and do not present pockets in which the galvanizing metal may collect.

' Consequently I prefer to form up the plates of Figure 6 from uncoated sheets or plates of metal by corrugating and curving them and perforating them where desired, and subsequently to galvanize them and/or otherwise treat them to prolong their life.

In forming up my culverts or conduits 4as hereinabove indicated, I employ a plurality of the curved and corrugated plates, hereinabove described, together with suitable fastening means such as bolts or rivets to hold said plates together, and where desired, suitable means for joining together adjacent sections of conduit as formed. The work of joining the plates and sections together is most advantageously done on the job in heavy construction. This facilitates shipping, and I am thus enabled to nest as shown in Figure 1, a plurality ofthe formedV and galvanized plates, which I have here indicated at I b, in

a stack, whereby space requirements are greatly cut down.

In the construction of these plates for the reasons hereinabove, I can use, (because I can successfully corrugate and bend) metal sheets and plates heavier than those heretofore used in the commercial manufacture of corrugated conduit. My invention`facilitates the use of arange of gauges of metal `from the heaviest now used to very much heavier gauges for the manufacture of large sized conduits, which range lof gauges is equivalent in scope to the range of gauges heretofore in common use for culverts or conduits, say of 54 inches-in diameter and under. I may and I prefer to use a configuration of the corrugation larger in its dimensions than that heretofore used for commercial culvert; and for culverts of different sizes, I may employ different sizes of corru'gations. This however is not a preferred practice for the reason that it involves a multiplication of manufacturing equipment and I therefore prefer to select a corrugation size suitable for use with the heavy metal pieces to which my invention is addressed and to meet strength requirements where necessary by gauge variations. I

also prefer and for most purposes I have found it entirely practicable to make but two or three different typesr of corrugated and curved plates, from which two or three types my invention permits me to build up culverts or conduits of a largenumber of dierent sizes, some of which sizes have peculiar advantages. In one commercial'example of my invention, I may make up two different types of plates.- Each will have the same type and size of corrugations so as to be capable of production upon a single machine. The two types of plates will diler from each other to have a length upon the arc equivalent to a 5 quadrant of a circle plus an allowance for overlap, by using four plates having a 45 inch radius, I may make as in Figure 9 a conduit section having a diameter of inches. I have indicated in Figure 9 plates having a radius of curvature of 10 45 inches by the letter A. I may also take four plates having a radius of curvature of say 30 inches and by joining these together in fours, I may make conduit sections having a diameter of 60 inches. In Figure 8 I. have indicated plates 15 having a radius of 30 inches by the letter B. I

` may form an elliptical culvert having an internal make up additional sizes of culverts' or conduits 25' by using some plurality of plates other than four,

'as will be evident.

In forming upa completed culvert from the plates hitherto described, I prefer to lap and join the plates in such a way that the bottom plate 30 laps inside the two adiacent side plates. When this is done, and when the members are fastened together with. separable fasteners as herein set forth, a singular advantage of the construction is that a bottom plate which has become worn or 35 damaged may be removed and a new plate inserted and fastened vin its place without disturbing the installation of the culvert.

The elliptical culvert of Figure 8 in addition to being useful as an intermediate size of con- 40 duit capable of being made of standard A and B sections, has additional structural advantages.

It has been demonstrated that the inherent strength of corrugated conduit resides in its exibility. When 'a corrugated conduit is loaded 45 from above, it deects, i. e., it flattens very slightly. When it is embedded in earth or the like as in culvert construction this flattening pushes the sides of the conduit outwardly thereby decreasing the pressure upon the 'top and increas- 50 ing the pressure upon the sides. In this way the pressure al1 about a condui-t becomes equa-lized through the flexibility of the conduit itself, and

The deflection of the culvert under load there-35 fore tends to cause the culvert to assume a more truly circular form rather than an elliptical form with the major axis horizontal, which form would obviously be weaker under top loads. Thus the ellipticalculvert of Figure 8 has distinc-t advan- 70 tages where it is intended to support top loads of considerable magnitude.

While I may, by a setting of my bending rolls, specially produce curved plates having radii of curvature specica'lly calculated for culverts 75 withstand abrasion internally as in culvert work,

I may with advantage make the lowermost stave or staves forming the bottom of the culvert of heavier metal than the remaining staves. Or I may otherwise specially prepare them. I may employ if desired, an invert vpaving in the lowermost stave or staves which paving may be built into some of the staves at the point of manufacture. the staves being assembled on the job in their proper relationship. Drainage'. structures deteriorate rst in the invert or iioor due to the effects of hydraulic trailic. 'I'hus the upper parts of a culvert have a relatively longer life because they are not so intensively -subjected to erosive and corrosive action. 'I'he bottom of the structure may therefore advantageously receive added protection, as by an invert paving, or be made of heavier material, or of more durable material.-

The more durable material may be of a different analysis from the material of the sides and top of the conduit so as to gain greater abrasion and corrosion resistance. Among the more durable materials which I may thus employ is a stainless iron or steel. Stainless metal, under present manufacturing conditions is too expensive in most uses to permit the fabrication of the entire conduit therefrom; but my novel construction is especially adapted to the formation of a conduit of ordinary iron or steel and an invert or bottom stave of stainless iron or steel.

The plates may be fastened together by riveting if desired, but where their assembly is effected on the job, I prefer to use bolts. Since the plates are preferably perforated before galvanizing, the bolts advantageously may be of a selfcentering type. I have shown in Figure l one type of bolt which has been found satisfactory. It comprises a head I, a' shank 8, and a threaded portion 9 on the end of the shank. The outer diameter of the threaded portion is preferably less than the outer diameter of the shank 8 so A that the threaded portion may be inserted in the holes of plates A and B without damage to the threads even if the perforations are slightly out of line. A nut I0 is provided having a flange portion II hollowed out interiorally so as to t over the shank 8. 'I'he tightening of the nut I0 will force the plates over lthe shank 8 with the perforations in the plates in alignment. I have shown in Figure 11 another suitable type of bolt having a head I2'and a shank I3 which in this instance is tapered and terminates in a threaded portion Il as shown. A nut I of ordinary Itype is employed an'd a split sleeve I6, the internal bore of which is tapered, is placed over the shank I3 after the bolt has been inserted through the holes'in the plates Afand B. With this type of bolt it is preferable to employ a washer I1, the ends of which are turned down to contact the plate A. A tightening of the nut I5 results in a flattening of the washer and a forcing of the sleeve I6 further up upon the shank I3 of the bolt, bringing the perforations in plates A and B into exact alignment.

If a uid tight joint is required between staves,

welding may-of course, be resorted to in place of, or in addition to other types of fastening, or the seams may be suitably provided with a fluid excluding member or construction.

With bolts of the class described or other suit- 5 able fastening means my plates are fastened together to form a culvert or conduit of the desired size and conguration. This may be done at the point of manufacture; but as hereinbefore explained, due to the difliculty of shipping built 10 up conduit in large size, it is in most instances convenient to assemble the plates on the job. When-sections are assembled, they are joined together to form a completed conduit of the required length. One method of making joints between sections is illustrated in Figure 4 in which the plates or staves indicated respectively at Ib and Ic are assembled in offsetrelationship so that at one end of a section the ends of plates Ib extend beyond the ends of plates I c Whereas the ends of plates Ic extend beyond the plates Ib at the other.` In joining sections,the plates Ib of one section of culvert are those bolted to the plates Ic of an adjoining section of plate. 'I'he amount of overlap may be varied but it should be at least suiiicient to produce a joint of the required strength. Two full corrugations is usually sufficient overlap; but the overlap may be increased up to one half the length of the plates' in the individual sections. This type of joint is strong and easy to produce but it requires at the startand nish, some plates of less than st andard length, and it also has the disadvantage that the edges of longitudinal contiguous staves do not overlap unless special provision is made for this. Thus in some instances it is preferable to employ instead or in addition a type of joint in which an external band encircles the joint between sections. I have shown in Figure 2 adjacent sections made up of plates I b and Ic which sections are 40 placed together in endwise alignment and are encircled by a band which -may be tightened on the joint. The band is corrugated so as to coincide with and fit over the corrugations of adjacent conduit sections, and it is Wide enough so as to engage and hold by its corrugations the corrugations of the adjacent sections. It is convenient to form such bands in sections each comprising the corrugated body I8 and flanges attached near the ends thereof. This construction is shown in Figure 3 where the flanges are indicated at I8.

They are bolted, welded or otherwise fastened to the corrugated body I8 'and the upstanding portions thereof are perforated as at 20 for the reception of boltsA 2| whereby the band maybe 55 assembled and tightened. The body section I8 of the band may be perforated at suitable .intervals vfor the reception of bolts 22 whereby it may be fastened to the conduit sections.

Having thus described my invention, 'what I 60 claim as new and desire to secure by Letters Patentis:

1. A process of forming. con'ugated conduit sections which comprises roll-corrugating rectangular metal plates heavier than 8 gauge with 65 the corrugations parallel to the shorter dimension thereof, perforating the edges of said plates for the passage of fastening members, bending said plates by means of a die to an arcuate shape subtending less than 180 galvanizing said plates, 70 and fastening the said plates together.

2. A corrugated conduit not less than inches in diameter comprising not less than four corrugated plates of heavier than 8 gauge metal joined together at their edges to form the circum'- 75 ference of a section thereof, the said plates of metal having a longer and shorter dimension and being corrugated with the corrugations running in the shorter dimension, the said plates being joined together along their longer edges and being curved, said joiningV comprising lapping of one edge over an edge of next plate a plurality oi said sections being included in the length of said conduit, and, the bottom plate of each section having both edges lapped inside of the other plates.

3. A process of forming corrugated conduit sections which comprises roll corrugating rectangular metal pieces heavier than 8 gauge with the corrugations parallel to the shorter dimension of said pieces, perforating the edges of said pieces for the passage of fastening members, bending said pieces by 'means of a die transversely to said corrugations to an arcuate shape subtending less than 180 degrees of arc, and fastening the said pieces together.

4. A corrugated conduit of large diameter'and for heavy duty, capable of being built up in a field, said conduit being not less than 60 inches in diameter and comprising not less than four corrugated plates of metal heavier than eight gauge j joined together in lapping relationship to form the circumference of said conduit at any given point throughout its length, the said plates of metal having a longer and shorter dimension and being corrugated with the corrugations running -in the direction of the shorter dimension, the said plates being joined together along their longer edges and being curved, said conduit being longer than the length of any one plate and having adjacent plates lengthwise of said conduit joined bylapping relationship, said joints being in break-joint relationship circumferentially, the ends of said conduit being formed in part by plates of full length and uplates of less than full length, whereby the ends of all plates at the end of said conduit terminate substantially in a single transverse plane, said conduit being characterized by continuous longitudinal seams and the plates forming the bottom or invert of said conduit when in use being lapped in said continuous seams inside of the adjacent sidewise plates.

5. A corrugated conduit of large diameter and for heavy duty, capable of being built up in a field, said conduit being not less than 604 inches in diameter and comprising notless than four corrugated plates of metal heavier than eight gauge joined together in lapping relationship to form the circumference of said conduit at any given point throughout its length, the said plates of metal having a longer and shorter dimension and being corrugated with the corrugations running in the direction of the shorter dimension, the said plates being joined together along their longer edges and being curved, said conduit being longer than the length of any one plate and having adjacent plates lengthwise of said conduit joined in lapping relationship, said joints being in breakjoint relationship circumferentially, the ends of said conduit being formed in part by plates of full length and plates of less than full length,- whereby the ends of all plates at the end of said conduit terminate substantially in a single transverse plane, said conduit being characterized by continuous longitudinal seams and the plates forming the bottom or invert of said conduit when in use being lapped in said continuous seams inside of the adjacent sidewise plates, said bottom forming plates being of heavier metal than the remainder of the plates in said conduit. .6. A corrugated conduit of large diameter and for heavy duty, capable of being built up in a field, said conduit being not less than 60 inches 5 in diameter and comprising not less than four corrugated plates of metal heavier than eight gauge joined together in lapping relationship to form the circumference of said conduitat any given point throughout its length, the said plates 10 of metal having a longer and shorter dimension and being corrugated with the corrugations running in the direction of the shorter dimension, the said plates being joined together along their longer edges and being curved, said conduit being longer than the length of any one plate and having adjacent plates lengthwise of said conduit joined by lapping relationship, said joints being in break-joint relationship circumierentially, the ends of said conduit being formed in part bygo plates of full length and plates of less than full length, whereby the ends of all plates at the end of said conduit terminate substantially in a single transverse plane, said conduit being' formed of plates of diiering radii of substantially circular curvature whereby said conduit is given a continuous elliptical shape throughout its length. Y.

7. A corrugated conduit of large diameter and `for heavy duty, capable of being built up in a iield, said conduit being not less than 60 inches in diameter and comprising not less than four corrugated plates of metal heavier than eight. gauge joined together in lapping relationship to form the circumference of said conduit at any 85 given point throughout its length, the said plates Y of metal having a longer and shorter dimension and being corrugated with the corrugations running in the direction of the shorter dimension, the said plates being joined together along ltheir 40 longer edges and being curved', said conduit being longer than the length of any one plate and having adjacent plates lengthwise of saidv conduit joined in lapping relationship, said joints being in break-joint relationship circumferentially, theA ends of said conduit .being formed in part by plates of full length and plates o f less than iull length, whereby the ends of all plates at the end. of said conduit terminate substantially in a single transverse plane, said conduit being characterized by continuous longitudinal seams and the plates forming the bottom or invert of said conduit when in use being ylapped in said continuous seams inside of the adjacent sidewise plates, said bottom forming plates being of heavier metal .55

' than the remainder of the plates in said conduit,

said conduit being formed of plates of differingradii of substantially circular curvature, whereby said conduit is given a continuous elliptical shape throughout its length. j

8. A process of forming sections for a heavy duty conduit, i. e. of heavier than 8 gauge metal, and having a diameter of more than inches, which comprises roll-corrugating rectangular sheets of metal in the direction of their' shorter dimension, submitting the corrugated sheets to a progressive series of curving impulses, perforating the edges of said sheets for the passage of fastening members, and galvanizing said sheets.

9. A corrugated sheet metal conduit for heavy duty installations comprising a plurality of rectangular sheets corrugated and curved in the direction of their shortest dimension, two opposed 75 rection of their shorter dimension, two opposed pairs of said sheets forming the circumference of said conduit, the pair forming the sides having a radius of curvature larger than the pair forming the top and bottom, said sheets being V joined together in lapped relation, the edges of the bottom sheet being lapped inside the edges of the adjacent side sheets.

JONATHAN ROY FREEZE. 

